I started by picking a font, making it as large as possible, and then cutting them out.
Then I traced it onto cardboard (from a soda can box... it was a little thin so I doubled up.)
Then I pulled out the trusty glue gun and chose my yarn. I went with blue this time. To make things a little simpler I wound smaller amounts of yarn that would pass through the spaces in the letters easier. I also cut a bunch of pieces about an inch long to cover the ends.
Take the smaller bundles of wool and start wrapping :) Depending on the letters you use, some will be easier than others. The most challenging of the 3 I did today was the "B". As you run short of yarn glue it in place on the back with at least half an inch at the end to tuck under. Glue the end of the new bundle and then cover it as you wrap. When you have covered the whole letter, use a needle to tuck in the end.
If you'd like these letters for yourself, check out whoopdwhoop.com and request them:) I'm making them available in any color!